Refractory



. Patented Mar. 10, 1936 UNITED STATES 'aosasss REFRACTORY Walter M.Farnsworth, Canton, Ohio, assignor to The Republic Steel Corporation,Youngstown, Ohio, a corporation of New Jersey No Drawing. ApplicationOctober 3, 1933, Serial No. 692,040

Claims.

This invention relates to refractories adapted for building, repairingor lining apparatus, pots, and furnaces subjected to high temperatures,such as electric metallurgical furnaces.

Heretofore, refractories have been more or less definitely classified inthree classes. The first of these classes is that of acid refractorieswhich are particularly adapted to resist'the scoring and corrosiveaction of acid material, such as acid slag, in metallurgical Work. Theseacid refractories are generally employed for roofs or arches of hightemperature furnaces in that they function to resist high temperaturesalthough they do not satisfactorily resist serious fiuxing reactions.Typical acid refractories are silica brick, chrysolite, sand andganister. V

The second type of refractory material is called the neutral type.Neutral refractories are adapted to resist the action of neutralsubstances which are neither basic no-r acid. Typical neutralrefractories include graphite, chromite, fire clay, carbon brick and thelike and they are employed for example in a basic open hearth furnace asan interposed layer between the roof of an acid refractory and thehearth of a basic refractory. This interposed layer terminatesordinarily slightly above the hearth lined with basic material so thatthe molten contents of the furnace will not attack the neutralrefractory. Moreover, if the basic and acid refractories are placed incontact with each other a reaction resulting in melting may occur.

The third class of refractories is that of basic refractory materialssuch as dolomite, which is 5 a magnesian lime stone, periclase,magnesite, Magnefer, which is a trade name for a calcined dolomite, etc.These basic refractories are employed for example in the hearth of thebasic open hearth furnace where other refractories 40 would be quicklyscored and corroded by the basic slags.

From the foregoing it will be recognized that refractory materialsheretofore had to be selected very carefully from the proper class andin view of the relation in which the same was to be employed in order toprevent premature scoring and corrosive action on the refractories andin order to eliminate frequent replacements. The difficulty of selectingrefractory materials for no particular use is very evident in theselection of refractories for electric furnaces employed in theproduction of steel. These electric furnaces are ordinarily of theinduction or are type and are particularly adapted to the manufacture ofstainless and other chrome steels in that the particular chrome andcarbon content necessary for these steels can be produced therein whichproduction is diflicult, and in many cases impossible, in open hearthfurnaces.

' The basic lined electric arc furnace for the production of steel isordinarily lined heavily with magnesite or Magnefer on the bottom, whileabove the slag line silica brick is employed for the side Walls, doorjambs, arches and roof of the furnace. Certain portions of the walls andjambs are apt to be cut or worn away so that patching of the furnacebecomes necessary. This patching operation was formerly accomplished bymixing ground magnesite with some suitable binding material such aswater glass, pitch or the like and then attempting to burn this patchingmaterial into the place to be repaired.

It was found that patching jobs performed in this manner, althoughhighly satisfactory from a refractory standpoint, were not the mosteconomical from the standpoint of furnace operation. The high prolongedtemperature required for bonding the magnesite made it impractical topatch with such material, particularly where the holes were deep for itwas essential that the next charge of metal be placed in the furnace aspromptly as possible after the prior head had been tapped. If magnesiteand the ordinary binding material were used a long time was required forbonding.

By the present invention an improved refractory substance is providedwhich can be employed for patching work such as in electric furnaces andwhich can likewise be employed as original linings or in otherrefractory relations as will be understood. The refractory of thepresent invention comprises a combination of magnesite, olivine andchrome ore. Magnesite is a double burnt or sintered magnesium oxidehaving certain oxides of calcium and iron present. The magnesium oxidecontent is ordinarily about 85%. Olivine is a form of chrysolite whichis relatively inexpensive and which can be readily obtained fromextensive deposits in the United States. It is a magnesium silicate ofiron having a typical chemical formula: (MgFe)2SiO4. A common sample ofolivine indicated the following general components (or elements whichwould form their equivalents): about 48% MgO, about 42% S102, about FeO.The chrome ore or chromite is a double oxide of iron and chromium andordinarily includes a little gangue. Its chemical formula is FeOCrzOa.

In the foregoing composition the magnesite is 55 the essentialrefractory material and the olivine and chrome ore supply the fluxing orbonding ingredients. I believe that the olivine reacts with the chromeore to produce a readily fusible substance and that either suchsubstance of the olivine soaks into the magnesite grains and makes themagnesite more readily fusible. The small sized particles of olivinecontact with much of the surface of the magnesite grains and thus canreadily soak into those grains before any tendency for it to run outdevelops. Chrome ore serves the additional function of stabilizing anydicalcium silicate which may be formed when a lime slag comes intocontact with the patching material.

By mixing the foregoing refractory materials in certain definiterelations a new and improved refractory material will result. The exactproportions in which the materials can be combined may varyconsiderably. However, a typical mixture consists of two parts by weightof olivine, three parts by weight of magnesite and one part by weight ofchrome ore. The olivine is in a finely comminuted form and distributedthroughout the mixture for the purpose of having the olivine in contactwith substantially all of the outer surface of the magnesite grains.This mixture was particularly adapted for use in electrical arc furnaceswhere it could be employed in conjunction with a Water glass binderwhich assisted in fusing the materials together in such a manner thatWash outs were prevented and the furnace was found to last for manyextra heats.

In employing the refractory substance in an electric induction furnacethe mixture was made dry and in the proportion of two parts magnesite,two parts chrome ore and one part olivine. The composition describedabove for use in electrical arc furnaces has likewise been found verysuccessful in induction furnaces as it fuses very hard, does not crackor spall off and resists knocking and scraping action occasioned bycharging the furnaces.

It will be appreciated that the mixture can be applied quiteadvantageously in paste form to the article or in the pot or furnace inwhich it is to be used, either as a lining or a repair patch.

The invention contemplates replacing the magnesite with a purer form ofmagnesium oxide such as periclase, which is crystallized magnesium oxideof about 90% purity. The refractory material produced from thiscombination is similar to that produced from magnesite but is slightlymore refractory. The periclase is bonded together by the remainingconstituents in the mix ture and tendency for wash outs or otherfailures is considerably reduced resulting in longer furnace life.

While the invention has been described as comprising a mixture ofolivine, chrome ore, and magnesite or periclase, which substances arerespectively acid, neutral and basic refractories, it is Within thescope of the invention to replace the specified materials with othermaterials from their general class which will function in a similar.manner to the specified materials named herein.

The refractory material produced in accordance with the teachings of thepresent invention has been particularly described as adapted for use inelectric metallurgical furnaces, however, it should be understood thatthe invention contemplates employing the material in substantially anyarticle or furnace subjected to high temperatures. It will, therefore,be appreciated that the foregoing description has, in accordance withthe patent statutes, specifically described certain forms andapplications of the invention, but that the scope thereof is not solimited but is defined in the appended claims.

What I claim is:

l. A refractory consisting of about 2 parts by weight of olivine, about1 part by weight of chrome ore, and about 3 parts by Weight of calcinedmagnesite.

2. A refractory substance resistant to lime slag reactions consisting ofabout 2 parts by weight of olivine containing about 48% MgO, about 42%SiOz and about 10% FeO, about 1 part by weight of chromite and about 3parts by weight of magnesium oxide.

3. A refractory consisting of about 1 part by weight of olivine, about 2parts by weight of calcined magnesite and about 2 parts by weight ofchrome ore.

4. A refractory substance resistant to lime slag reactions consisting ofabout 1 part by weight of olivine containing about 48% MgO, about 52%S102 and about 10% FeO, about 2 parts by weight of a magnesium oxide andabout 2 parts by weight of chromite.

5. A refractory containing between about 2 and 3 parts by weight of arefractory substance containing above magnesium oxide, between about 1and 2 parts by weight of olivine containing between 48% MgO, about 42%SiOz and about 10% FeO, and about 1 part by weight of chrome ore, saidrefractory substance being bonded together with the chrome ore andolivine, said olivine being finely comminuted and distributed throughoutthe mixture.

WALTER M. FARNSWORTH.

